This is the push-hands sequence of Wardoff, Rollback, Press and Push. The action is that of sawing. When you saw, the force at both sides should be equal; then the action is smooth. If one side tries to change the force, the saw’s teeth will bind. If my partner binds the saw, then even if I were to use force I would not be able to draw it back. Only if I push it will saw smoothly as before. This has two meanings for the push-hands of T’ai Chi Ch’uan. The first is to give up oneself to follow others. In following the opponent’s tendency you can learn the marvelous application of hua chin (neutralization) and tsou chin (yielding). Second, “If others move slightly, I move first.” This refers to the situation wherein my opponent uses force to push me and I obviate his attack by pulling back first. If the opponent uses pull I preclude this by pushing first.
The principle in the example of pulling the saw brings great clarity. Through it, I suddenly comprehended how to practice the idea, “if others move slightly, I move first.” If I am familiar with this, then the push-hands is controlled by me and not by my opponents. The rest is obvious.

( Red.: It’s said; “If the other does not move, I do not move. If the other has the slightest movement, I move ahead” proverb taken from the Taiji Classic “The understanding of the Thirteen Postures” )